I shot at a concert for the first time. The pictures were pretty good for the capability of my equipment, but on some shots, the light has a very strange flare. It isn't the usual rays, but some soft, non-symmetric form which I find quite strange, and, on most shots, distracting.

On this image, you can see it just above Gino's head and also behind his back, to the right of the mic stand. I am not sure if the slight blue lines on the left side of the picture (they form a triangle aimed at Chris's head, maybe not visible on all monitors) are part of the problem or if they come from a different light source.

What makes them appear, and how do I avoid them?

I shot with a D90 with a 18-200 lens, no filters or hoods attached. The settings were quite strained (iso 3200, often at max length and max aperture for the length. This specific picture is 1/125, f 5.3, 95 mm).

3 Answers
3

If you're talking about the strange arcs like in the bottom left corner of this picture:

Then it's just flare caused by shooting into a lightsource. Concert lights tend to produce strong flaring effects as they are very focussed.

The only fix is to use a different lens (they all flare differently) or not shoot directly into any lightsources. However when I'm shooting concerts I usually shoot directly into the lights on purpose and use any flare as an artistic tool to make the image more interesting.

Here's another image featuring some particularly strange flare from the Canon 50 f/1.8:

Thank you. I didn't know that it is the same thing I have seen manifested as small dots until now (I was even afraid to use the term "flare" in the question, thinking it might be misleading). But better to know that there isn't anything I can do (short of buying a lens) than worrying for being too bad at shooting. And you are right, on some pics (including the one I uploaded) they don't look too bad.
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rumtschoAug 17 '11 at 19:33

what configuration you have think in mind to get an effect like the last one with the C50?
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LeandroMay 20 '13 at 13:40

All cameras contain lenses which are actually comprised of several "lens elements." Lens flare is caused by non-image light which does not pass (refract) directly along its intended path, but instead reflects internally on lens elements any number of times (back and forth) before finally reaching the film or digital sensor

A good lens hood can nearly eliminate flare caused by stray light from outside the angle of view. Ensure that this hood has a completely non-reflective inner surface, such as felt, and that there are no regions which have rubbed off. Although using a lens hood may appear to be a simple solution, in reality most lens hoods do not extend far enough to block all stray light. This is particularly problematic when using 35 mm lenses on a digital SLR camera with a "crop factor," because these lens hoods were made for the greater angle of view. In addition, hoods for zoom lenses can only be designed to block all stray light at the widest focal length.

Petal lens hoods often protect better than non-petal (round) types. This is because petal-style hoods take into account the aspect ratio of the camera's film or digital sensor, and so the angle of view is greater in one direction than the other.Placing a hand or piece of paper exterior to the side of the lens which is nearest the flare-inducing light source can also mimic the effect of a proper lens hood.

Lens flare also depends on the lens used - fixed focal length (or prime) lenses are less susceptible to lens flare than zoom lenses. Other than having an inadequate lens hood at all focal lengths, more complicated zoom lenses often have to contain more lens elements. Zoom lenses therefore have more internal surfaces from which light can reflect.

Your other choice is to use a hood. That will help avoid the flares from off the frame.

It also appears that the flare is accentuated by some CA as well. Stopping down a little or using a brighter lens that is better corrected may help.

Lastly, don't use UV filters indoors/at night unless they are multi-coated to remove such reflections. When in use, they provide two additional surfaces for flaring. It's better to leave them off in these situations.

Still, having flares used for dramatic/visual effect (eg: Star Trek) is in vogue. If you like this look, do all the reverse!